Polyester resins are well known thermoplastic materials which, due to their many advantageous physical properties, find use as thermoplastic engineering materials in many commercial and industrial applications. These resins, for example, exhibit excellent properties of toughness, flexibility, impact strength, heat resistance, chemical resistance and excellent surface appearance. In some cases these polyesters also have good barrier properties. Such resins may generally be prepared by the reaction of a dihydric alcohol and a dicarboxylic acid or chemical equivalent thereof.
For some specialized applications, i.e. automotive parts, it is important that such resins have enhanced chemical resistance to aggressive solvents, for example, acetone, aromatic solvents, gasoline, and the like, to a degree which may not be necessary in most other applications. We have found that blends of polyesters and amorphous polyamides have the excellent solvent resistance required for this application.
Although polyesters such as polyethylene terephthalate are currently used in packaging applications special processing to orient the material is necessary in order to obtain good barrier properties. It has now also been discovered that addition of amorphous polyamide to the polyesters improves barrier properties without the need for orientation.